A hybrid vehicle and an electric vehicle having an electric motor to be used as a drive source have been conventionally known. Power is supplied to the electric motor from a battery mounted on the vehicle. Power stepped up by, for example, a converter is supplied to the electric motor. An electric circuit for supplying the power to the electric motor is provided with capacitors such as a filter capacitor for eliminating noise and a smoothing capacitor for smoothing a voltage.
Although the capacitors effectively function when the vehicle travels, electric charges reserved in the capacitors are not needed during stoppage of the vehicle. If the electric charges are reserved for a longer period of time than necessary, this may bring about an adverse effect such as promotion of degradation of the capacitors. In view of this, there has been proposed a technique for electrically discharging the capacitors.
Japanese Patent Laying-Open No. 2004-201439 (PTL 1) discloses a voltage conversion system that can consume electric charges reserved in a capacitor without using an electric discharge resistance. The voltage conversion system is provided with a power supply, an inverter, a voltage converter, first and second capacitors, and a controller. The voltage converter is connected between the power supply and the inverter. The first capacitor is inserted onto the power supply side in the voltage converter whereas the second capacitor is inserted onto the inverter side in the voltage converter. The controller controls the voltage converter in such a manner as to consume residual electric charges in the first capacitor and residual electric charges in the second capacitor in response to a stop signal.